Heretofore, various patches have been developed in order to improve the skin permeability of a drug contained in the patches. For example, patches are known on which attempts are made to improve the skin permeability of a drug by making the drug itself into a free form. As an example of such patches, Japanese Unexamined Patent Application Publication No. Sho 62-126119 (PTL 1) discloses a patch using a combination of an organic acid and a non-steroidal anti-inflammatory analgesic agent having a salt form of an alkali metal in order to improve the solubility of the drug.
Moreover, patches are known on which attempts are made to improve the skin permeability of a drug by incorporating an organic acid and/or an organic acid salt together with the drug. For example, International Publication No. WO01/07018 (PTL 2) discloses a patch containing a basic drug, an organic acid, and an organic acid salt. PTL 2 discloses acetic acid, lactic acid, and the like as the organic acid, and sodium acetate and the like as the organic acid salt.
However, such patches as disclosed in the cited literatures 1 and 2 have problems that an organic acid added at the time of production is likely to volatilize, accordingly decreasing the production stability, and that the skin permeability decreases over time as a result of the organic acid volatilization. Further, for example, International Publication No. WO2005/115355 (PTL 3) discloses a patch containing a basic drug and a volatile organic acid, and discloses that the patch further contains an organic acid salt in consideration of the amount of the organic acid to be lost by volatilization. Nevertheless, even such a patch is still insufficient in production stability, skin permeability, and stability over time of the skin permeability.
Meanwhile, asenapine is a compound known as a drug for use in the treatment of central nervous system diseases, particularly schizophrenia. Patches containing asenapine are disclosed, for example, in International Publication No. WO2010/127674 (PTL 4) and so forth.